The embodiment described herein relates generally to real time condition monitoring of Li-Ion batteries. The battery impulse response is utilized to estimate the State-Of-Health (SOH) of a Li-Ion battery and to distinguish among possible faults which may occur inside the battery.
Several conventional methods and systems exist for estimating SOH and the parameters effecting the health status of Li-Ion batteries, but they all have some drawbacks. A common battery monitoring method is the full or partial discharge test where the battery is discharged by subjecting the battery to a constant current load. During the discharge, the voltage of the battery is measured and the time it takes to drop to a certain voltage is compared with that of a healthy battery as a means for estimating the health of the battery under test. Besides being expensive and time consuming, the full or partial discharge test damages the battery since routine and deep battery discharge can reduce the life of the battery. Additionally, the test has to be done while the battery is off-line and its accuracy depends on the depth of the discharge.
Another method for estimating the SOH of lead acid batteries uses the coup de fouet phenomenon. In this method, the magnitude of the voltage drop during the early minutes of battery discharge correlates with the SOH of the battery. As the battery ages, the battery encounters a loss of active material utilization caused by various processes such as sulfation and changes in pore structure. These changes result in a decrease of the available battery capacity and thus as the battery ages, the coup de fouet voltage is lowered. Although this method is a quick and simple technique for estimating SOH of the battery, it cannot be done online and additionally requires a constant load for performing the discharge test.
Yet another conventional method for estimating the SOH of batteries involves ohmic techniques including impedance, resistance, and conductance measurements. Measuring the internal resistance of the battery is very sensitive to measurement error and the accuracy of the measurement highly depends of the way the contact is made between the battery terminals and the lead of the ohmic meter. Additionally, none of the ohmic technique methods are efficient for real time estimation of SOH while the battery is under load and the required measurements are not always available in general applications.
The embodiment or embodiments described herein may solve these shortcomings as well as others by proposing a novel method of online SOH estimation of chemical batteries, such as Li-Ion, Ni-MH, Ni—Cd, and Lead-acid, using the concept of battery impulse response.